Rafts, as we have already remarked, must undoubtedly have been the beginning of navigation. But they have not, like many other species of ancient craft, been altogether superseded by modern inventions. True, we do not nowadays carry on war on rafts, but we still carry on trade with them in many parts of the world. How the rafts of ancient times were formed we cannot tell precisely, though we can easily guess; but one thing we know, and that is, that the first improvement made in such craft was the thrusting of a few thick planks down into the water, to the depth of three or four feet, between the logs which composed the raft. These acted the part of a keel, and, by pressing against the water _side-ways_ when a _side_ wind blew, prevented the raft from making much of what is called _leeway_--that is, drifting in the direction in which the wind happened to be blowing. Some sorts of Dutch vessels use lee-boards for this purpose at the present time. The rafts now in use on the great rivers of America are exceedingly curious in many respects. One peculiarity of many of them is that they float _themselves_, not goods, to market--the pine logs of which they are constructed being the marketable commodity. Some of these "lumber-rafts," as they are called, are of great size; and as their navigators have often to spend many weeks on them, slowly floating down the rivers, they build huts or little cottages on them, cook their provisions on board, and, in short, spend night and day in their temporary floating-homes as comfortably as if they were on the land. When these rafts approach a waterfall or a rapid, they unfasten the lashings and allow several logs tied together to run down at a time. After the rapid is passed, the loose logs are collected together, the raft is reconstructed, and the voyage down to the sea continued. Of course, huts are built only on rafts which navigate the largest rivers, and are not thus liable to be taken to pieces. When the logs reach the sea, they are shipped to various parts of the world where timber is scarce. Large quantities are imported into Great Britain from Canada and other parts of America. A bold thing has occasionally been done. Instead of shipping the logs in vessels, enterprising and ingenious men built them into a _solid ship_, leaving a small space to serve as a cabin and a hold for provisions; then, erecting masts, they hoisted sail, and in this singular craft crossed the Atlantic. On arriving at port they broke up their raft-ship and sold it. The immense size of the rafts which are floated down some of the great rivers of the world may be gathered from the following engraving, which represents a raft on the Dwina, one of the great rivers of Russia.